#include <iostream>
#include <vector>
using namespace std;

void countDown(int count) {
    cout << "push " << count << endl;
    countDown(count - 1);
}

// don't run, causes infinite recursion!
countDown(5)

void countDownAgain(int count) {
    cout << "push " << count << endl;
    if (count > 0)
        countDownAgain(count - 1);
    else
        cout << "stop recursion" << endl; // base case
    cout << "pop " << count << endl;
}

long factorial(long n) {
    if (n <= 1)
        return 1;
    return n * factorial(n-1);
}

long fibonacci(long n) {
    if (n < 2) return n;
    return fibonacci(n-1) + fibonacci(n-2);
}

int vectorSum(vector<int> v) {
    if (v.empty()) return 0;
    int last = v.back();
    v.pop_back();
    return vectorSum(v) + last;
}

class Node {
    public:
        int data;
        Node *left;
        Node *right;
        Node(int d) {
            data = d; 
            left = nullptr; 
            right = nullptr;
        }
}

// create a bnary tree
auto root = new Node(1), n2 = new Node(2), n3 = new Node(3), 
    n4 = new Node(4), n5 = new Node(5);
root->left = n2;
root->right = n3;
n2->left = n4;
n3->right = n5;

// height of a node?
int treeHeight(Node * n) {
    if (n == nullptr)
        return -1;
    // if (n->left == nullptr && n->right == nullptr) {

    // }

    int leftHeight = treeHeight(n->left);
    int rightHeight = treeHeight(n->right);
    if (leftHeight > rightHeight)
        return leftHeight + 1;
    else
        return rightHeight + 1;
}